storage: flash map: Add FIXED_PARTITION(label) macro

The commit adds FIXED_PARTITION(label) macro that allows to obtain
struct flash_area object for partition of given label.
The macro allows instantiation of partition at point of usage
and will be replacing need for defining flash map with all partition
entries.
Area obtained with the macro should not be passed to open, instead
flash_area_device_is_ready, basically equivalent of device_is_ready
should be called on the obtained pointer to check if area is ready
for use.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>

include/zephyr/storage/flash_map.h

@@ -133,6 +133,28 @@ int flash_area_open(uint8_t id, const struct flash_area **fa);
  */
 void flash_area_close(const struct flash_area *fa);
 
+/**
+ * @brief Verify that a device assigned to flash area is ready for use.
+ *
+ * Indicates whether the provided flash area has a device known to be
+ * in a state where it can be used with Flash Map API.
+ *
+ * This can be used with struct flash_area pointers captured from
+ * FIXED_PARTITION().
+ * At minimum this means that the device has been successfully initialized.
+ *
+ * @param[in] fa pointer to flash_area object to check.
+ *
+ * @retval true If the device is ready for use.
+ * @retval false If the device is not ready for use or if a NULL pointer is
+ * passed as flash area pointer or device pointer within flash area object
+ * is NULL.
+ */
+static ALWAYS_INLINE bool flash_area_device_is_ready(const struct flash_area *fa)
+{
+	return (fa != NULL && device_is_ready(fa->fa_dev));
+}
+
 /**
  * @brief Read flash area data
  *
@@ -376,6 +398,31 @@ uint8_t flash_area_erased_val(const struct flash_area *fa);
 #define FIXED_PARTITION_NODE_DEVICE(node) \
 	DEVICE_DT_GET(DT_MTD_FROM_FIXED_PARTITION(node))
 
+/**
+ * Get pointer to flash_area object by partition label
+ *
+ * @param label DTS node label of a partition
+ *
+ * @return Pointer to flash_area type object representing partition
+ */
+#define FIXED_PARTITION(label)	FIXED_PARTITION_1(DT_NODELABEL(label))
+#define FIXED_PARTITION_1(node)	FIXED_PARTITION_0(DT_DEP_ORD(node))
+#define FIXED_PARTITION_0(ord) (const struct flash_area *)&DT_CAT(global_fixed_partition_ORD_, part)
+
+/** @cond INTERNAL_HIDDEN */
+#define DECLARE_PARTITION(part) DECLARE_PARTITION_0(DT_DEP_ORD(part))
+#define DECLARE_PARTITION_0(part)						\
+	extern const struct flash_area DT_CAT(global_fixed_partition_ORD_, part);
+#define FOR_EACH_PARTITION_TABLE(table) DT_FOREACH_CHILD(table, DECLARE_PARTITION)
+
+/* Generate declarations */
+DT_FOREACH_STATUS_OKAY(fixed_partitions, FOR_EACH_PARTITION_TABLE)
+
+#undef DECLARE_PARTITION
+#undef DECLARE_PARTITION_0
+#undef FOR_EACH_PARTITION_TABLE
+/** @endcond */
+
 #ifdef __cplusplus
 }
 #endif

subsys/storage/flash_map/flash_map_default.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 Nordic Semiconductor ASA
+ * Copyright (c) 2017-2024 Nordic Semiconductor ASA
  * Copyright (c) 2015 Runtime Inc
  * Copyright (c) 2023 Sensorfy B.V.
  *
@@ -43,3 +43,21 @@ const struct flash_area default_flash_map[] = {
 
 const int flash_map_entries = ARRAY_SIZE(default_flash_map);
 const struct flash_area *flash_map = default_flash_map;
+
+/* Generate objects representing each partition in system. In the end only
+ * objects referenced by code will be included into build.
+ */
+#define DEFINE_PARTITION(part) DEFINE_PARTITION_1(part, DT_DEP_ORD(part))
+#define DEFINE_PARTITION_1(part, ord)								\
+	COND_CODE_1(DT_NODE_HAS_STATUS_OKAY(DT_MTD_FROM_FIXED_PARTITION(part)),			\
+		(DEFINE_PARTITION_0(part, ord)), ())
+#define DEFINE_PARTITION_0(part, ord)								\
+	const struct flash_area DT_CAT(global_fixed_partition_ORD_, ord) = {			\
+		.fa_id = DT_FIXED_PARTITION_ID(part),						\
+		.fa_off = DT_REG_ADDR(part),							\
+		.fa_dev = DEVICE_DT_GET(DT_MTD_FROM_FIXED_PARTITION(part)),			\
+		.fa_size = DT_REG_SIZE(part),							\
+	};
+
+#define FOR_EACH_PARTITION_TABLE(table) DT_FOREACH_CHILD(table, DEFINE_PARTITION)
+DT_FOREACH_STATUS_OKAY(fixed_partitions, FOR_EACH_PARTITION_TABLE)